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#241910 - 25/11/2004 10:42 Re: Deciphering Amp specs [Re: scollinguk]
frog51
pooh-bah

Registered: 09/08/2000
Posts: 2091
Loc: Edinburgh, Scotland
I'm going to have to weigh in here on Genixia's side - as a lot of my background is in design (both power and audio electronics) so I know a wee bit about it.

As Genixia says, the heatsink size is actually a very good indicator of power output (with some tweaks such as amplifier class and forced air induction vs convection etc needing to be taken into account) whereas in designing amplifiers some years back our fuse choice was almost always a "what stock have we got that is around about right to avoid component destruction?" not actually to do with power output as such. In some circumstances there was a correlation, but in general it was more down to what parts we had or could get hold of easily.

And even there, it will only give you an upper bound for sustained power. Peak may be way over - dependent on whether you have a fast blow or slow blow.

Amusingly, I'm actually pretty sure the 30 Amp fuse I have for my amp in the car would blow if I turned things way up, but as it is slightly overspec'ed I keep it down around 2 or 3 and get no distortion/clipping and it is still too loud to shout over. Should probably know better, but ten, I don't want to be deaf, so think it's safe as it is.
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#241911 - 25/11/2004 12:11 Re: Deciphering Amp specs [Re: scollinguk]
bonzi
pooh-bah

Registered: 13/09/1999
Posts: 2401
Loc: Croatia
Quote:
PS RMS is an acronym for "root mean squared", where the exact output of the amplifier is recorded across a range of inputed signals and then there square root is applied to the results, then the mean average is taken and that mean average is then squared.

Err, the other way around, I am affraid: first square, then mean, then root. That way you avoid those pesky complex numbers.

Actually, in the context of amplifiers, it is continuous power calculated from measuring RMS voltage while driving resistive load with harmonic (sinusoidal) signal (for prescribed time with prescribed maximal distortion etc). You could measure peak voltage as well (as long as you know the shape of the signal), but the life is easier with the voltmeter that gives RMS (or effective) voltage.
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#241912 - 29/04/2005 15:53 Re: Deciphering Amp specs [Re: Mach]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
Quote:
...
The footprint and the digital input seem to make it a good fit for an empeg with one of Stu's sound cards, no?
...


Sorry to slew slightly off topic, here, but I'm new to the BBS and the world of empegs, so I'll take some n00b license and ask:
What's a 'Stu's sound card' and how does it relate to the empeg?
Is this a hack/upgrade?
I've spent a few minutes searching, but couldn't find any clear discussion of sound cards here...

And, slightly more on-topic- I'm looking for a small 4-channel amp to power stock-sized speakers... um, that's not really contributing, just clarifying my interest in the thread.
Thanks!
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#241913 - 29/04/2005 17:27 Re: Deciphering Amp specs [Re: Robotic]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31563
Loc: Seattle, WA
"Stu" is "Eutronix", follow the link at the top of the page and all will be answered.
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#241914 - 29/04/2005 18:53 Re: Deciphering Amp specs [Re: tfabris]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
Ah-so!
Thanks, Tony
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